Contrasting Roles of Islet Resident Immunoregulatory Macrophages and Dendritic Cells in Experimental Autoimmune Type 1 Diabetes

The innate immune system critically shapes diabetogenic adaptive immunity during type 1 diabetes (T1D) pathogenesis. While the role of tissue-infiltrating monocyte-derived macrophages in T1D is well established, the role of their tissue-resident counterparts remains undefined. We now demonstrate that islet resident macrophages (IRMs) from non-autoimmune mice have an immunoregulatory phenotype and powerfully induce FoxP3+ Tregs in vitro. The immunoregulatory phenotype and function of IRMs is compromised by TLR4 activation in vitro. Moreover, as T1D approaches in NOD mice, the immunoregulatory phenotype of IRMs is diminished as is their relative abundance compared to immunostimulatory DCs. Our findings suggest that maintenance of IRM abundance and their immunoregulatory phenotype may constitute a novel therapeutic strategy to prevent and/or cure T1D

Hematopoietic Stem/Progenitor Cell Dependent Participation of Innate Lymphoid Cells in Low-Intensity Sterile Inflammation

Hematopoietic stem/progenitor cells (HSPC) are characterized by their unique capacities of self-renewal and multi-differentiation potential. This second property makes them able to adapt their differentiation profile depending on the local environment they reach. Taking advantage of an animal model of peritonitis, induced by injection of the TLR-2 ligand, zymosan, we sought to study the relationship between bone marrow-derived hematopoietic stem/progenitor cells (BM-HSPCs) and innate lymphoid cells (ILCs) regarding their emergence and differentiation at the site of inflammation. Our results demonstrate that the strength of the inflammatory signals affects the capacity of BM-derived HSPCs to migrate and give rise in situ to ILCs. Both low- and high-dose of zymosan injections trigger the appearance of mature ILCs in the peritoneal cavity where the inflammation occurs. Herein, we show that only in low-dose injected mice, the recovered ILCs are dependent on an in situ differentiation of BM-derived HSPCs and/or ILC2 precursors (ILC2P) wherein high-dose, the stronger inflammatory environment seems to be able to induce the emergence of ILCs independently of BM-derived HSPCs. We suggest that a relationship between HSPCs and ILCs seems to be affected by the strength of the inflammatory stimuli opening new perspectives in the manipulation of these early hematopoietic cells

Thérapie cellulaire des maladies autoimmunes avec des populations de progéniteurs hématopoïétiques : caractérisation et comparaison de leur mécanisme d'action dans le diabète de type I et encéphalomyélite autoimmune expérimentale

It is well known today that various infectious events or other stimuli of the immune system can trigger hematopoiesis. The hematopoeitic stem and/or progenitor cells express on their cell surface Toll-like receptors which can recognize molecular motifs of infectious agents. The stimulation of TLRs on hematopoietic stem cells favors their differentiation into myeloid lineages, reinforcing the capacity of our body to fight against the pathogens. Herein, we have investigated whether the stimulation of TLRs can induce, instead, the emergence within the bone marrow of selective progenitor cells with immunoregulatory properties. We show that incubation of bone marrow cells with the TLR-9 ligand CpG-B can induce a pro-B cell population (named CpG-proBs) whose adoptive transfer at low numbers of 60,000 cells provided long-lasting protection in two models of autoimmune diseases, Type I Diabetes (TID) and Experimental Autoimmune Encephalomyelitis (EAE) at the onset of clinical signs. The migration, differentiation and molecular mechanism of action of this protective population is described and compared between these two models. In both models, the CpG-proBs migrate to the target tissue of autoimmune responses and differentiate into more mature regulatory B cells. In TID, IFN-γ produced by both T and CpG-proB cells is essential for the upregulation of FasL at the surface of CpG-proBs, inducing the apoptosis of the effector T cells. In addition, IFN-γ reduced the T-cell production of IL-21, a major pathogenic cytokine in TID. The progeny of the adoptively transferred CpG-proBs, including transitional precursors B cells, marginal zone and follicular B cells, display high expression of FasL, promote apoptosis of effector T cells and prolong the control of autoimmune effector T cells in vivo. In EAE, IFN-γ was responsible for the restriction of T cells to the lymph nodes, inhibiting their homing to the CNS. IFN-γ indirectly induced the internalization of CCR7, a receptor required for the migration across the blood-brain barrier. In the spinal cord (target tissue in EAE), CpG-proBs differentiated into B220+CD5+CD1dhiCD11b+ cells secreting the anti-inflammatory cytokine IL-10. Finally, hematopoietic progenitor populations mobilized to the periphery by a cocktail of G-CSF and Flt3l, at the stage of MPP2, have already been shown to protect against TID by expanding the Foxp3+ Tregs. We evaluated them in the EAE model, showing that the ability of these mobilized progenitor cells to trigger the expansion of Foxp3+ Treg within the CNS and the periphery was necessary for providing protection to EAE mice since Treg depletion abrogated the protection once established. In conclusion, we provide evidence for the emergence of new populations of hematopoietic progenitor cells which can display immunoregulatory properties and might be used for cell therapy of autoimmune diseases.Les infections et l’activation du système immunitaire stimulent l’hématopoïèse. L’activation des récepteurs Toll-like (TLRs) des cellules souches hématopoïétiques, par leur reconnaissance de motifs moléculaires portés par des agents infectieux, en oriente la différenciation vers les voies myéloïdes, renforçant la capacité de notre organisme à lutter contre les infections. Ici, nous avons étudié si les agonistes TLRs peuvent, au contraire, induire au sein de la moelle osseuse l’émergence de progéniteurs hématopoïétiques présentant des propriétés immunorégulatrices. Nous montrons que l’incubation de moelle osseuse de souris en présence de l’agoniste TRL-9, CpG-B, entraîne l’émergence d’une population de progéniteurs au stade pro-B (appelée CpG-proBs). Le transfert adoptif de seulement 60,000 CpG-proBs par receveur, à l’apparition des premiers signes cliniques, confère une protection à long terme dans deux modèles expérimentaux de maladies auto-immunes, le Diabète de Type I (T1D) et l’Encéphalomyélite Auto-immune Expérimentale (EAE). La migration, la différenciation, et les mécanismes cellulaires et moléculaires de cette population protectrice sont décrits et comparés entre ces deux modèles. Dans les deux modèles, les CpG-proBs migrent vers le tissu cible de la réponse auto-immune et se différencient en cellules B matures régulatrices. Dans le T1D, l’interféron-γ (IFN-γ) produit par les cellules T s’avère essentiel pour induire la surexpression de FasL à la surface des CpG-proBs, entraînant l’apoptose des cellules T effectrices. De plus, l’IFN-γ produit par les CpG-proBs réduit la production par les cellules T de l’IL-21, une cytokine pathogène majeure dans le T1D. La descendance des CpG-proBs est composée de précurseurs transitionnels B, de cellules B de la zone marginale et de cellules B folliculaires, exprimant de forts niveaux de FasL et toujours capables d’induire l’apoptose des cellules T, prolongeant ainsi le contrôle des cellules effectrices T auto-immunes in vivo. Dans l’EAE, l’IFNγ est indirectement responsable de la rétention des cellules T, par l’internalisation de CCR7, au sein des ganglions lymphatiques, inhibant ainsi leur migration au système nerveux central (SNC). Dans la moelle épinière, tissu cible de l’EAE, les CpG-proBs se différencient en cellules B220+CD5+CD1dhiCD11b+, secrétant la cytokine anti-inflammatoire IL-10. Enfin, la mobilisation des progéniteurs hématopoïétiques par un cocktail de facteurs hématopoïétiques confère à une sous-population multipotente au stade MPP2 la propriété d’augmenter l’expansion des Foxp3+ Tregs et de prévenir la survenue du diabète de type 1. Nous montrons que les MPP2 mobilisés s’avèrent également capables d’exercer un effet protecteur envers l’EAE. Leur capacité à induire l’expansion de Treg Foxp3+ au sein du SNC et à la périphérie joue un rôle essentiel dans la protection des souris envers l’EAE, puisque la déplétion des Treg abolit la protection déjà établie. Pour conclure, nous avons mis en évidence que diverses stimulations de l’hématopoïèse induisent l’émergence de nouvelles populations de progéniteurs hématopoïétiques qui présentent des propriétés immunorégulatrices et constituent de nouveaux outils de thérapie cellulaire des maladies auto-immunes

Thérapie cellulaire des maladies autoimmunes avec des populations de progéniteurs hématopoïétiques (caractérisation et comparaison de leur mécanisme d'action dans le diabète de type I et encéphalomyélite autoimmune expérimentale)

Les infections et l activation du système immunitaire stimulent l hématopoïèse. L activation des récepteurs Toll-like (TLRs) des cellules souches hématopoïétiques, par leur reconnaissance de motifs moléculaires portés par des agents infectieux, en oriente la différenciation vers les voies myéloïdes, renforçant la capacité de notre organisme à lutter contre les infections. Ici, nous avons étudié si les agonistes TLRs peuvent, au contraire, induire au sein de la moelle osseuse l émergence de progéniteurs hématopoïétiques présentant des propriétés immunorégulatrices. Nous montrons que l incubation de moelle osseuse de souris en présence de l agoniste TRL-9, CpG-B, entraîne l émergence d une population de progéniteurs au stade pro-B (appelée CpG-proBs). Le transfert adoptif de seulement 60,000 CpG-proBs par receveur, à l apparition des premiers signes cliniques, confère une protection à long terme dans deux modèles expérimentaux de maladies auto-immunes, le Diabète de Type I (T1D) et l Encéphalomyélite Auto-immune Expérimentale (EAE). La migration, la différenciation, et les mécanismes cellulaires et moléculaires de cette population protectrice sont décrits et comparés entre ces deux modèles. Dans les deux modèles, les CpG-proBs migrent vers le tissu cible de la réponse auto-immune et se différencient en cellules B matures régulatrices. Dans le T1D, l interféron-g (IFN-g) produit par les cellules T s avère essentiel pour induire la surexpression de FasL à la surface des CpG-proBs, entraînant l apoptose des cellules T effectrices. De plus, l IFN-g produit par les CpG-proBs réduit la production par les cellules T de l IL-21, une cytokine pathogène majeure dans le T1D. La descendance des CpG-proBs est composée de précurseurs transitionnels B, de cellules B de la zone marginale et de cellules B folliculaires, exprimant de forts niveaux de FasL et toujours capables d induire l apoptose des cellules T, prolongeant ainsi le contrôle des cellules effectrices T auto-immunes in vivo. Dans l EAE, l IFNg est indirectement responsable de la rétention des cellules T, par l internalisation de CCR7, au sein des ganglions lymphatiques, inhibant ainsi leur migration au système nerveux central (SNC). Dans la moelle épinière, tissu cible de l EAE, les CpG-proBs se différencient en cellules B220+CD5+CD1dhiCD11b+, secrétant la cytokine anti-inflammatoire IL-10. Enfin, la mobilisation des progéniteurs hématopoïétiques par un cocktail de facteurs hématopoïétiques confère à une sous-population multipotente au stade MPP2 la propriété d augmenter l expansion des Foxp3+ Tregs et de prévenir la survenue du diabète de type 1. Nous montrons que les MPP2 mobilisés s avèrent également capables d exercer un effet protecteur envers l EAE. Leur capacité à induire l expansion de Treg Foxp3+ au sein du SNC et à la périphérie joue un rôle essentiel dans la protection des souris envers l EAE, puisque la déplétion des Treg abolit la protection déjà établie. Pour conclure, nous avons mis en évidence que diverses stimulations de l hématopoïèse induisent l émergence de nouvelles populations de progéniteurs hématopoïétiques qui présentent des propriétés immunorégulatrices et constituent de nouveaux outils de thérapie cellulaire des maladies auto-immunes.It is well known today that various infectious events or other stimuli of the immune system can trigger hematopoiesis. The hematopoeitic stem and/or progenitor cells express on their cell surface Toll-like receptors which can recognize molecular motifs of infectious agents. The stimulation of TLRs on hematopoietic stem cells favors their differentiation into myeloid lineages, reinforcing the capacity of our body to fight against the pathogens. Herein, we have investigated whether the stimulation of TLRs can induce, instead, the emergence within the bone marrow of selective progenitor cells with immunoregulatory properties. We show that incubation of bone marrow cells with the TLR-9 ligand CpG-B can induce a pro-B cell population (named CpG-proBs) whose adoptive transfer at low numbers of 60,000 cells provided long-lasting protection in two models of autoimmune diseases, Type I Diabetes (TID) and Experimental Autoimmune Encephalomyelitis (EAE) at the onset of clinical signs. The migration, differentiation and molecular mechanism of action of this protective population is described and compared between these two models. In both models, the CpG-proBs migrate to the target tissue of autoimmune responses and differentiate into more mature regulatory B cells. In TID, IFN-g produced by both T and CpG-proB cells is essential for the upregulation of FasL at the surface of CpG-proBs, inducing the apoptosis of the effector T cells. In addition, IFN-g reduced the T-cell production of IL-21, a major pathogenic cytokine in TID. The progeny of the adoptively transferred CpG-proBs, including transitional precursors B cells, marginal zone and follicular B cells, display high expression of FasL, promote apoptosis of effector T cells and prolong the control of autoimmune effector T cells in vivo. In EAE, IFN-g was responsible for the restriction of T cells to the lymph nodes, inhibiting their homing to the CNS. IFN-g indirectly induced the internalization of CCR7, a receptor required for the migration across the blood-brain barrier. In the spinal cord (target tissue in EAE), CpG-proBs differentiated into B220+CD5+CD1dhiCD11b+ cells secreting the anti-inflammatory cytokine IL-10. Finally, hematopoietic progenitor populations mobilized to the periphery by a cocktail of G-CSF and Flt3l, at the stage of MPP2, have already been shown to protect against TID by expanding the Foxp3+ Tregs. We evaluated them in the EAE model, showing that the ability of these mobilized progenitor cells to trigger the expansion of Foxp3+ Treg within the CNS and the periphery was necessary for providing protection to EAE mice since Treg depletion abrogated the protection once established. In conclusion, we provide evidence for the emergence of new populations of hematopoietic progenitor cells which can display immunoregulatory properties and might be used for cell therapy of autoimmune diseases.PARIS5-Bibliotheque electronique (751069902) / SudocSudocFranceF

TLR1/2 orchestrate human plasmacytoid predendritic cell response to gram+ bacteria

International audienceGram+ infections are worldwide life-threatening diseases in which the pathological role of type I interferon (IFN) has been highlighted. Plasmacytoid predendritic cells (pDCs) produce high amounts of type I IFN following viral sensing. Despite studies suggesting that pDCs respond to bacteria, the mechanisms underlying bacterial sensing in pDCs are unknown. We show here that human primary pDCs express toll-like receptor 1 (TLR1) and 2 (TLR2) and respond to bacterial lipoproteins. We demonstrated that pDCs differentially respond to gram+ bacteria through the TLR1/2 pathway. Notably, up-regulation of costimulatory molecules and pro-inflammatory cytokines was TLR1 dependent, whereas type I IFN secretion was TLR2 dependent. Mechanistically, we demonstrated that these differences relied on diverse signaling pathways activated by TLR1/2. MAPK and NF-κB pathways were engaged by TLR1, whereas the Phosphoinositide 3-kinase (PI3K) pathway was activated by TLR2. This dichotomy was reflected in a different role of TLR2 and TLR1 in pDC priming of naïve cluster of differentiation 4+ (CD4+) T cells, and T helper (Th) cell differentiation. This work provides the rationale to explore and target pDCs in bacterial infection

The metabolic enzyme fructose-1,6-bisphosphate aldolase acts as a transcriptional regulator in pathogenic Francisella

The enzyme fructose-bisphosphate aldolase occupies a central position in glycolysis and gluconeogenesis pathways. Beyond its housekeeping role in metabolism, fructose-bisphosphate aldolase has been involved in additional functions and is considered as a potential target for drug development against pathogenic bacteria. Here, we address the role of fructose-bisphosphate aldolase in the bacterial pathogen Francisella novicida. We demonstrate that fructose-bisphosphate aldolase is important for bacterial multiplication in macrophages in the presence of gluconeogenic substrates. In addition, we unravel a direct role of this metabolic enzyme in transcription regulation of genes katG and rpoA, encoding catalase and an RNA polymerase subunit, respectively. We propose a model in which fructose-bisphosphate aldolase participates in the control of host redox homeostasis and the inflammatory immune response

Mobilized Multipotent Hematopoietic Progenitors Stabilize and Expand Regulatory T Cells to Protect Against Autoimmune Encephalomyelitis

International audienceAchieving immunoregulation via in vivo expansion of Foxp3+ regulatory CD4+ T cells (Treg) remains challenging. We have shown that mobilization confers to multipotent hematopoietic progenitors (MPPs) the capacity to enhance Treg proliferation. Transcriptomic analysis of Tregs co-cultured with MPPs revealed enhanced expression of genes stabilizing the suppressive function of Tregs as well as the activation of IL-1b–driven pathways. Adoptive transfer of only 25,000 MPPs effectively reduced the development of experimental autoimmune encephalomyelitis (EAE), a pre-clinical model for multiple sclerosis (MS). Production of the pathogenic cytokines IL-17 and GM-CSF by spinal cord-derived CD4+ T-cells in MPP-protected recipients was reduced while Treg expansion was enhanced. Treg depletion once protection by MPPs was established, triggered disease relapse to the same level as in EAE mice without MPP injection. The key role of IL-1bwas further confirmed in vivo by the lack of protection against EAE in recipients of IL-1b–deficient MPPs. Mobilized MPPs may thus be worth considering for cell therapy of MS either per se or for enrichment of HSC grafts in autologous bone marrow transplantation already implemented in patients with severe refractory multiple sclerosis